1. Field of the Invention
Embodiments of the present invention relate generally to speaker systems and methods, and in specific embodiments, to speaker systems for musical instruments that detect displacement of the voice coil, and process such displacement information in feedback to alleviate non-linear distortion, in which the user has control over the amount of motion feedback applied.
2. Related Art
In speaker systems for audio use, motional feedback (hereinafter referred to as “MFB”) is known in which the displacement of the voice coil of a speaker or the displacement of a sensor cap and the like is detected. The detected displacement is used as a difference value with the input signal as negative feedback, and the difference value is amplified by a power amplifier to drive a speaker.
It is known that the non-linear movement of the speaker is vastly improved by means of this MFB processing. In Japanese Laid-Open Patent Application Publication (Kokai) Number H 10-276492, which is incorporated herein by reference in its entirety, an MFB speaker system is disclosed in which the output of a filter to which the displacement that has been detected and the sound signal are supplied is averaged, and an abnormal sound is avoided, even in those cases where the center of the voice coil oscillation displacement has shifted.
However, in the MFB speaker systems of the past, although it is possible to improve the non-linear speaker movement, such systems have been impractical for musical instruments, because it is not possible to actively set the characteristics such as the timbre and the like of the musical tones that are produced.
In prior speakers for musical instruments that produce many low tones such as a bass guitar and the like, or musical instruments that have a wide tonal range like a piano, when the low tones are reproduced, the amplitude of the mechanical oscillation of the voice coil and the cone paper of the speaker is great. As a result, because non-linear distortion is produced and high amplitude sounds hit a peak, it has not been possible to satisfactorily carry out dynamic expression. Because of this, the performer may tend to feel that he or she must perform more forcefully in order to make the musical tones that have been produced by one's own performance better.